Soil-borne invertebrate pests, i.e., arthropods (crustaceans, arachnids, and insects) and nematodes, cause untold billions of dollars worth of damage throughout the world to crops, dwellings, and structures useful to humankind. Soil-borne insects attack the seeds and seedlings of most crops. For example, black cutworm (Agrotis ipsilon-Hufnagel) commonly feeds on seedlings of, for example, corn, at ground level, cutting off the stem and sometimes dragging the plants into their burrows. Most of the plant is not consumed but merely eaten enough to cause it to topple. Since the larvae occur burrowed near the roots of the host, it sometimes feeds on roots and the below-ground stem. Because of the nature of their feeding on young plants, this pest can do great damage in newly planted fields. Corn plants that are too large for larvae to cut through may have a hole bored into the stem. Large populations can decimate an entire field of corn seedlings. Yield losses to uncontrolled black cutworm can be as high as 25%.
Nematodes are among the most destructive plant-parasitic soil-borne organisms on a wide range of plants. For example, sting nematodes (Beloizolainus longigicaudatus) are ectoparasites of plant roots, where they remain in the soil and feed by inserting a long stylet or mouth spear into root tips. The nematodes then inject enzymes into root tissues and suck plant juices out through the stylet. Root tips typically cease growing in response to feeding by sting nematodes. Sting nematodes cause particular damage to young plants with a developing root system. Sting nematodes cause yield losses in many crops and can cause complete crop destruction with severe infestations. Damaged crops include vegetables (carrot, corn, crucifers, beans, potato, etc.), fruits (citrus, strawberry, etc.), agronomic crops (cotton, peanut, sorghum, soybean, etc.), turfgrasses (Bahiagrass, Bermudagrass, St. Augustinegrass, zoysiagrass, etc.) and forest crops (pine trees).
Termites, however, are undisputedly the most destructive of all soil-borne invertebrate pests. Termites are estimated to cause 1.5 billion dollars of damage to wooden structures and dwellings annually, and that an additional one billion dollars is spent on treatment. Depending on the type of termite, a colony can cover as much as 22,000 square feet. These industrious insects work 24 hours a day, gradually eating wood and any other cellulose containing material in their environment. Since they remain hidden within the wood in which they are feeding, in mud tubes, or in the soil, they typically wreak havoc undetected. There are two types of termites, described as i) dry wood termites, and ii) subterranean termites. Of these two types, the subterranean termites usually live in the soil (i.e., soil-borne), from which they build mud tubes to structural wood where they then feed.
Control of soil-borne invertebrate pests can be accomplished by strategic application of at least one invertebrate pest-control agent to the soil in a locus where there is an invertebrate pest infestation. When the invertebrate pest is termites, a standard method for placing the termiticide in the soil is by physical means. Such physical means include, inter alia, (1) the digging of trenches around the outside of a structure, then flooding the trenches with termiticide, or (2) by injecting the termiticide directly into the soil using a mechanical device, such as a soil rod. These methods are very labor-intensive, and require an inordinate amount of termiticide to be effective. Another method for control of soil-borne termites is by the application of a termiticide directly to the surface of soil, thereby in theory creating a chemical barrier in the soil when the termiticide leaches into the soil.
Invertebrate pest control agents having utility in application directly to the surface of soil are in the form of liquid invertebrate pest control agents. A liquid invertebrate pest control agent is defined as a composition comprised of a formulation containing an invertebrate pest control agent where the formulation is dispensed in an aqueous medium prior to its application to a locus where invertebrate pest control is needed. For example, a liquid termiticide is therefore defined as a composition comprised of a formulation containing a termiticide where the formulation is dispensed in an aqueous medium prior to its application to a locus where termite control is needed.
Examples of formulations that can be dispensed in aqueous medium to provide a liquid invertebrate pest control agent include, without limitation, formulations of bifenthrin, sold by FMC Corporation under the names and trademarks of TALSTAR® GC FLOWABLE INSECTICIDE/MITICIDE, or TALSTAR® TERMITICIDE/INSECTICIDE. However, the invertebrate pest control agent in most liquid invertebrate pest control agents prepared from these formulations are not particularly mobile in the soil. That is to say, the invertebrate pest control agent does not appreciably spread downwardly and laterally from its point of application on the surface of the soil. Reasons for the immobility of such invertebrate pest control agents when placed on the soil include, inter alia, (1) the limited water solubility of the invertebrate pest control agent, for example, of about 3 parts per million (ppm) or less, and (2) the tendency of the invertebrate pest control agent to bind to the soil. Consequently when a liquid invertebrate pest control agent containing such relatively water-insoluble, soil-binding invertebrate pest control agents are applied to the soil, there may be gaps, or thinly treated areas, in the desired continuous chemical barrier caused by the immobility of the invertebrate pest control agent in the soil. Soil-borne insects such as termites, therefore, can gain access to food sources/structures through gaps and thinly treated areas in the chemical barrier. To aid in providing the continuous chemical barrier in the soil, a method and/or compositions of liquid invertebrate pest control agents that promote increased downward and lateral movement of relatively water-insoluble, soil-binding invertebrate pest control agents is clearly needed.